Background: Although most patients with gastrointestinal stromal tumor (GIST) treated with imatinib mesylate achieve remission or disease stabilization, a significant proportion show progressive disease (PD) with or without initial favorable responses. We evaluated and categorized the patterns of progression of metastatic or unresectable GIST treated with imatinib to identify the prognostic significance and contribution to further treatment decision-making.
Methods: We prospectively gathered clinical data from 62 GIST patients treated with imatinib mesylate (400 mg/day) over a median period of 26 months. Twenty-one of these patients showed evidence of PD based on Response Evaluation Criteria in Solid Tumor criteria.
Results: Four patterns of PD were defined: focal progression (FP, N = 4), general progression (GP, N = 6), new cystic lesion (NCL, N = 6) and new solid lesion (NSL, N = 5). The groups were found to differ in terms of time to progression and prior response to imatinib. The proportion of patients who responded to escalated doses of imatinib (600-800 mg/day) was significantly higher in NCL patients (P = 0.04). Overall survival and survival from the confirmation of PD were significantly better in NCL or FP patients compared with NSL or GP patients (P = 0.0157, P = 0.0013).
Conclusions: We identified four patterns of disease progression based on radiographic criteria with different clinical characteristics and impact on survival. Knowledge of these patterns was relevant for early detection and may be helpful in further treatment decision-making.